I officially quit this shop. They truly can not figure this out. According to them this is as good as it gets. This car has been to them over a dozen times. We did virtually all parts of the AC system. It worked great then they screwed it up.

They claim they found a leak in a long AC hose (said it was about 3 feet). Replaced this. I just drove home, and same thing. Cool at revs but warms quickly at idle.

I hate to go somewhere else and start paying again but I just can not deal with these people anymore.

Any suggestions would be good. The only thing that changed was them doing motor mounts. Something must have been knocked out of place.

If anyone is aware of a decent shop in Las Vegas, I would be interested.

If it worked great at some point recently then it can be fixed...Hang in there... has to be something logical...Did they flush the condensor and evaporator ? Could it be in the controls or sensors ? Maybe they are dirty or misadjusted .. do you have the temp sensor on the dash ?

Have you checked for correct operation of your thermovalve, if you have one ? Greg

when they replaced the hose what did they refill the system with? Sure it was r12 and not 134? If it blows cold when moving but warms at an idle it sounds like it was refilled with 134a. By law if they used 134a there should be a sticker that says that, along with new quick connect fittings.
Also overcharging or undercharging the system will also give you these symptoms.

A tiny bit undercharged is preferable to any overcharging...
OK, if they put in 134 but did not put the stickers or attach the valves which they should have.... how would one check to see which refrigerant was in ones system ? any home tests ?and if they put in 134 instead of 12 when your oils were the ones for 12 I wonder how long it will be before adverse permanent damage is done ? But really , we are stretching here... check for vacuum/actuators/sensors/controls first....since all those other things were done... Greg

Just payed another shop to diagnose. Fully charged with R12. They found no leaks or problems so essentially assumed that the problem must be the expansion valve. Since they say the cannot get right to this it must be the problem through the process of elimination.

They also claim that the dryer needs to be replaced each time the system is opened up. Is this accurate?

Do you all think this second shop is correct?

if the expansion valve is going bad or has a bunch of junk stuck in it you should be able to see it on the gauges. Low side will drop below normal and the high side will go above. Also if you look at the valve it should be frosted up at the point of the blockage, in this case right before the valve and the valve will be iced if there is considerable blockage. As far as replacing the drier yes and no. If it is old and the system has been opened up then yes it must be replaced. If it is fairly new and the system has not been discharged or open for a long time then it does not have to replaced. If the shop that just replaced your hose didn't evacuate the system and pull a strong vacuum for at least a half hour you may have moisture in the system that is causing ice to clog at the expansion valve.

Can you help me with checking this? I do not even know what it looks like or where it is. I would like to be able to confirm that the expansion valve has issues.

on my 83 you remove the kick pannel on the rt. hand side. There is a siver block about 2" long to the left of the blower. You should see the pipes going in and out from this block. One side will be cool the other side warm to hot. The silver block will feel cool or even cold but should not be iced up. The expansion valve will always be as close as possible to the evaporator. I have never changed one out on a MB but it looks like it would be pretty easy to get to.

Technically this is a combination valve. It is a single block which has the expansion valve and the thermosyphon valve in it . The latter is used to make sure the evaporator does not go below 32 degrees f so that you will not have moisture frozen on the outside which would stop the flow of air across the evaporator fins... I just got one a few weeks ago from Phil.... at Fastlane..best price I found... for my 1980 240d.... save the old one you take out... someone on the forum will want it to make a ac service tool out of it... like it says to do in the FSM...

The wrenches you will need to take it out are 17,19,20 and 24 mm and it helps to have a large cresent or water pump pliers to hold the body when you start tweaking the flare nuts... don't want to bend anything... Greg

1980 126? does it have a Monovalve? Failure mode is constant heat more at idle less at speed! could be counteracting the AC? Sudden onset of symptoms seems interesting.

If this car has one it's a quick and easy check:

http://mbdieseldiy.tripod.com/monovalve.htm

Good Luck!

On my 83 I have an inline filter. I don't think this was a stock item but I could be wrong. It's not on the 77. The PO had the entire system rebuilt when the compressor went and converted to 134a. I have heard that if the compressor blows and the system is left open for any length of time that a filter should be added to trap any dirt and rust that may form. I don't think these systems have the screen that most new cars have in front of the ex-valve. The opening in the valve is very small and it wouldn't take much to mess it up. Flushing the system out will remove most of this stuff but unless you replace everything you don't know what may have stayed in there and a filter is cheap insurance.
Also you can see the thermosyphon valve section. It is a little flat round disk looking thing with a sensor wire running into the evaporator core. Like Greg said it keeps the system from freezing up by opening and closing the expansion valve. If you determine this part is bad you will save yourself money by having a shop remove the r-12, get credit for it, and replace the parts yourself. It should not be a hard job, no special tools needed. After getting all back together have the same shop evacuate and re-fill the system.

rebootit,

It sounds like you are describing a suction side filter. This is a good thing to do in a system that has blown a compressor. Some people install this valve in lieu of flushing the system.

Good luck,

I think filters can be put on both sides.. the suction one would protect the compressor and the other one could protect the expansion valve...

I expect that the fact that this happened at the same time that the oil cooler lines were replaced is no coincidence. I fully expected that they simply knocked the clutch wire loose while working in that area. If it is a hose, I expect that they put some pressure on it while wrestling the oil cooler lines in place. With an old hose, too much pressure at the end of it could easily be just enough to make it turn loose. They should be able to make a new hose without too much trouble. Once repaired, given that you are in Vegas I would strongly recommend that you stay with R12.

Good luck,

Still no result. Expansion valve replaced. Not much improvement. Since every part has been replaced this isn't costing any more money but it is a hassle.

They are now wanting to replace the compressor thinking that the one we already did is bad. Apparently there is not enough head pressure???

Would this make a system blow cool; not cold?